Fuse plug



Jan. 19, 1932. sCHMlD-r, JR 1,841,638

FUS E PLUG Filed March 25, 1928 Patented Jan. 19, 1932 UNITED STATES PATENT OFFICE oL'AJMIBER/.l SCHMIDT, JR., 0F BROOKLYN, NEW YORK, ASSIGNOR TO HIMSELF .AND LOUIS FREUND, F NEW YORK, .N. Y.

FUSE PLUG Application tiled Hatch 23, 1928. Serial No. 264,263.

plug has at its outer end a manipulable member constructed and arranged to rotate the plug when turned in the direction to screw the plug into the socket, this member beingalso so constructed Vand arranged that when it is rotated in the opposite direction, in an effort to remove the plug, it rotates freely in vrelation to the plug, which therefore remains in the socket, protecting the socket terminals from being shorted by insertion of a metal 20 object or instrument. The manipulable member, when the plug is in the socket, is the only practicably accessible part of the plug,

and since its rotation is ineffective to remove the plug, unskilled or unauthorized persons find it practically impossible to remove the plug from the socket. Means is also provided by which authorized persons can remove the plug, such means preferably including a frnngible member and a formation of the plug adapted for engagement by a simple implement to rotate the same for removal from the socket after the frangible member is broken.

A further object is to practically or entiref ly prevent the use of a fuse plug to provide an improper connection between socket terminals by cutting and bending one of the plug contact members. For this purpose the usual threaded shell or screw constituting one of the. plug contacts, is replaced by a relatively narrow strip or segmental contact piece, which cannot practicably be manipulated or arranged to bridge the socket contacts.

l 45 The characteristics and advantages of the invention are further sufficiently explained in connection with the following detail description of the accompanying drawings, which show certain representative embodiments.

'D After considering these examples, skilled persons will understand that many variations may be made, and I contemplate the emplo ment of any structures that are proper y within the scope of the appended claims.

Fig. 1 is a plan view of a fuse plug embody- 55 ing the invention in one form, in positionm a socket.

Fig. 2 is a section at 2 2, Fig. 1.

Fig. 3 is a side elevation of the plug, with a part broken away.

Fig. 4 is a top plan of a plug of modified construction.

Fig. 5 is a side elevation of the same, with a part broken away.

In Figs. 1 and 2, 1 is any ordinary plug 35 socket having a threaded contact shell 2 and a central bottom contact 3, these contacts 'being connected, respectively, to terminals or binding posts 4 and 5, which are in turn connected to conductors 6 and 7 of the fused 70 circuit.

The plug body 8, of insulating material, has a central or fuse-recess 9, an end or bottom contact 10 to engage socket contact 3, and a side contact 11 to engage socket con- 75 tact 2. Contacts 10 and 11 are connected by the fuse strip 12 located in recess 9. As so far described the plug is of ordinary construction. Fuse plugs of this character are easily inserted in the socket, and as easily gg removed, by rotary or screw action, and unauthorized or unskilled persons may therefore remove the plug at any time, giving access tothe socket terminals. It is a quite common practice, when fuse 12 is blown 55 by an overload, and when a fresh fuse is not available, to remove the blown plug and bridge the socket terminals with a strip or piece of any available metal, which may sometimes beheld in place by reinsertion of the blown plug. Thus, for example, a coin may be placed in the socket and held in position to bridge the socket terminals by inserting the plug 8. Such make-shift or substitute connections in a main circuit are, of course, not calculated for proper maximum current flow, and upon occurrence of any overload will usually cause the blowing out of a number of local fuses or injury to electrical apparatus in the circuit, injury to the circuit conductors or their insulation, short 'circuits or ires.- Such make-shift fusing or ized persons and thus prevent access to the socket terminals and improper connection thereof in the manner above mentioned.

The plug body has at its u per or outer end a thick flange 15. A manipu able member 16, usually of sheet metal, is secured to the outer end of the plu by cooperation With flange 15. v

The manipula le member or ring 16,v includes an outer or end flange 17 overlylngthe outer end of the plug, a cylindrical or sleeve portion 18 overlying the periphery of flange 15, and an inturned flange or lip 19 underlying the inward face of flange 15. The member 16 is applied While the lip or flange 19 is 1n the form of a straight cylindrical extension of the sleeve portion 18, and the lip is then pressed or spun inward to engage under the plug flange and retain the ring permanently in position so that it cannot be removed Without destroying it. The ring has a slightly loose engagement With the plug; that is it is revoluble upon the plug, except as such rotation in one direction is prevented by means to be described.

The outer margin of the outer end 20 of the plug is provided with any suitable plurality of ratchet notches 2l, Fig. 3, each notch-including a bevelled portion and an axially directed shoulder 22, these notches being all similarly arranged in a circular direction. The outer flange 17 of 'the manipulable member or ring 16, is cut and pressed to provide one or more (usually two) inbent members or paWls 23. The sheet metal or ring 16 is resilient and the pawls 23 therefore resiliently engage the outer face 2() of the plug.

To insert the plug in the socket the periphery of ring 16 is grasped in the fingers, the end ol the plug is applied to the socket, and the ring is rotated clock-Wise, as viewed in Fig. 1. l'n this rotative movement the fingers or pawls 23 enter the ratchet notches 21 and their ends engage the shoulders 22, causing the plug to rotate along vwith the finger piece or ring for lirm insertion in the socket in the usual manner. If it is attempted, for any reason, to remove the plug by reverse rotation in the usual manner, the finger piece or ring 16 will rotate freely in a counter-clockwise direction, as viewed in Fig. l, the paWls or lingers 23 in this movement riding back over the inclines of the ratchet notches in the fashion of an ordinary ratchet device; or, in other Words, the linger piece is operatively disconnected from the plug and has no capacity to rotate it. Unauthorized persons, therefore, upon attempting to remove the plug, find it is impracticable to `tention of such do so by any ordinarily available means, or withoutdestroying the plug.

The outer end of the fuse recess 9 is ordinarily closed by a mica disc 25 located in a shallow face-recess 26 in the outer end of the plug= and retained by ametal fitting or rin similar to the ring 16, but not provlded with any means such as here disclosed to operatively connect the ring with the plug in one direction of rotation, and to operatively disconnect it in the other direction. My present ring and ratchet construction is adapted for the proper location and rea mica closure disc 25 y arranging the ratchet notches 2l and pawls 23 in outward marginal portions of the plug face and ring flange 17, respectively, so that the paWls are located outside the periphery ofthe mica disc, and the inner margin 27 of flange 17 overlies the outer margin of the disc and retains it permanently in position, secure against removal, except by breaking the disc or destructive injury to ring i6. The recess 9 is thus sealed and the inner members of the plug terminals are inaccessible for connection by a make-shift fuse or shortcircuiting device.

To enable the plug to be easily removed by authorized persons, means are provided by which the plug may be rotated in reverse or left-hand direction by application o a suitable tool or simple implement, usually after rupturing some part ol' the plug structure-preferably the mica cover disc Thus, in the present structures, the use recess 9, near its outer end, is provided with irregularities or has a polygonal socket formation, such as the square formation shown at 30,'Figs. 1 and a'. After breaking the mica seal 25, any convenient implement, such as the squared or flat end of a Wooden stick may be inserted into the polygonal formation 30 and the plug reversely rotated by this implement, after which a fresh plug may be inserted in the usual way.

T he outer Contact member ol' these plugs is usually in the form of a threaded shell of continuous or sleeve form, to engage the threaded socket shell 2. After a fuse is blown this )lucr contact or shell is sometimes cut and i prevent such unauthorizedor dangerous l manipulation of the plug, Whether or not it is provided with means such as above described for preventing its removal 'from the socket, l preferably substitute for the outer or shell contact, a notch or strip contact 40, Five 2 and 3, embedded in or overlying the side the plug in a longitudinal direction. This strip is usually threaded, as at 41, to correlill llt)

spond with the thread formation ol the socket shell 2, and since the strip or segment the lstrip 40 form segments of the complete annular screw threads. The lower end 43 of the contact piece may be embedded 1n the materlal of the socket 1n process ofmanufacture, and the upper portion 44 passes through the Socket wall for connection to one end of the fuse strip, as usual. The contact strip or piece 40 isso small that it is not practicably available for bridgingthe socket terminals by cutting and bending it in such a manner as above described.

Figs. 4 and 5 show a modification of the ratchet connection between the manipulable ring 16 and the plug body. In this arrangement the plug flange 15 has a peripheral `channel 50, in the inner face of which ratchet notches 51 are formed. Ring 16 is rovided with a ratchet device consisting o a piece of spring wire 52, bent to circular form and having one end connected to the sleeve portion 18 of the ring, as by soldering at 53, and to facilitate the soldering operation an aperture may be formed in the ring sleeve at thatvpoint. The other end of the spring wire is inbent to form a tooth or pawl 54 to cooperate with the ratchet notches 51 in substantially the same manner and for the same purpose as described with reference to Figs. 1 to 3.

Evidently other ratchet structures or arrangements may be provided, and other features of construction may be varied without departing from the principles disclosed.

A plug can be manufactured according to this invention at the same, or less expense,

than the ordinary plug not having the safety features disclosed herein.

I claim:

1. A plug adapted for insertion in an electric socket and having contacts to cooperate with the socket contacts, comprising a body, a manipulable member thereon accessible for grasping and insertion of the plug, and means by which rotation of the manipulable memf ber in one direction is effective to rotate the plug and produce engagement between the plug and socket contacts, and rotation of the manipulable member in the other direction is ineffective to rotate the plug or disconnect the plug and socket contacts.

2. A plug adapted for insertion in an electric socket and having contacts to cooperate ywith the socket contacts, comprising a body,

a manipulable member revolubly mounted on an outward portion ofthe plug, and means acting in one direction of rotation of said member to rotate the plug therewith, said means when said member is rotated in the reverse direction being ineffective to rotate the plug.

3. A plug adapted for insertion in an electric'soc et and having contacts to cooperate with the socket contacts, comprising a body, a manipulable member revolubly mounted on an outward portion of the plug, and ratchet mechanism intermediate the'plug body and said member to produce rotation of the body when the member is rotated in one direction -while permitting the member to be rotated in the opposite direction without rotative effect upon the plug body.

4. A safety fuse plug comprising a body having a fuse recess and contacts to cooperate with socket contacts, .a fuse in the recess connecting the plug contacts, a manipulable member loosely mounted on an outward portion of the lug, and means by which rotation of saidJ member in one direction produces corresponding rotation of the plug body and rotation of the member in the other direction is ineffective to rotate the plug body.

having a fuse recess and contacts to cooperate with socket contacts, a fuse in the recess connecting the plug contacts` a manipulable member loosely mounted on an outward portion of the plug, and means by which rotation of said member in one directionproduces corresponding rotation of the plug body and rotation of the member in the other direction is ineffective to rotate the plug body, the plug body having a'formation to cooperate with an implement for rotating the body in a direction to remove it from the socket.

6. A plug adapted for insertion in an electric socket and having contacts to cooperate with the socket contacts, comprising a body, a manipulable member thereon accessible for grasping and insertion of the plug, and means by which rotation of the manipulable member in one direction is effective to rotate the plug and produce engagement between the plug and socket contacts, and rotation of the manipulable member in the other direction .is ineffective to rotate the plug or disconnect the plug and socket contacts, the body having near its outer end a polygonal implementreceiving formation adapted to cooperat with an inserted implement by which the body ma be rotated and removed from the electric soc et. e

7. A safety fuse plug comprising a body having a fuse recess and contacts to cooperate with socket contacts, a fuse in the recess connecting the plug contacts, a manipulable member loosely mounted on an outward portion of the plug, and means by which rotation of said member in one direction produces corresponding rotation of the plug body and rotation of the member in the other direction is ineffective to rotate the plug` body, the fuse recess having near its outer end a polygonal socket formation adapted for cooperation 5. A safety fuse plug comprising a body l with an inserted implement fto rotate and remove the plug from the electric socket.

8. A safety use plug comprising a body having a fuse recess and contacts to cooperate with socket contacts, a fuse in the recess connecting the plug contacts, a frangible seal for the outer end of the recess, a manipulable member loosely mounted on an outward portion of the plug and means by which rotation of said member in one direction produces corresponding rotation` of the plug body and rotation of the member in the other direction is ineffective to rotate the plug body.

9. A safety "fuse plug comprising a body having a fuse recess and contacts to cooperate with socket contacts, a fuse in the recess con necting the plug contacts, a frangible seal for the outer end ot the recess, a manipulable member loosely mounted on an outward portion of the plug and means by which rotation of said member in one direction produces corresponding rotation of the plug body and lable member having'portions embracing the body flange and overlying the outer face of the body, the outer face of. the body being provided with ratchet notches, and the overlying portion of said manipulable member having ratchet members 'to cooperate with the notches.

14. A safety fuse plug comprising a recessed body having contacts to cooperate with socket contacts, a body having a flange at its outward end, and a sheet metal manipulable member having portions embracing the body tlange and overlying the outer tace of the body, the outer tace or the body being provided with ratchet notches, and the overlying portion of said manipulable member having portions cut and inbent to form pavvls to cooperate With the notches.

ln testimony whereof I aliik my signature.

LAMBERT SCHMlDT, Jn.

rotation of the member in the other direcd tion is ineffective to rotate the plug body, the fuse recess near its outer end having a loi-mation to cooperate with an implement inserted after rupture ot the itrangible seal, whereby the body may be rotated in a direction to remove it from the socket.

l0. A safety fuse plug comprising a recessed body having contacts to cooperate with socket contacts, a body having a flange at its outward end, an annular manipulable member revolubly mounted on the body in cooperation With the flange, and ratchet mechanism intermediate said member and the body, effective to rotate the body with said member when the latter is rotated in one direction, and inellective to rotate the body When the member is rotated in the opposite direction. l

ll. A safety fuse plug comprising a recessed body having contacts to cooperate with socket contacts, a body having a flange at its outward end` and a sheet metal manipulable member having portions embracing the body flange and overlying the outer face of the body, said member having revoluble engagement with the body, and ratchet means intermediate said member and the body.

12. A safety fuse plug comprising a recessed body having contacts to cooperate with socket contacts, a body having a flange at its outward end, an annular manipulable member revolubly mounted on the body in cooperation with the flange, an outer part of the body having ratchet notches, and one or more ratchet members carried by said member and adapted to cooperate with the notches.

13. A safety fuse plug comprising a recessed body having contacts to cooperate with socket contacts, a. body having a flange at its outward end, and a sheet metal manipu- 

